JP2001269862A - Polishing pad, polishing device, and polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and reliably detect the end point of the polishing of CMP or the like. SOLUTION: This polishing device is provided with a polishing board 101 fitted with a polishing pad 103 having a plurality of conduction parts 109 separated from each other in the planar direction, a hold part 104 holding a substrate to be processed 106 to face its polished face to the polishing board 101 fitted with the polishing pad 103, drive parts 102 and 105 relatively moving the polishing board 101 and the hold part 104, and a detection part 111 detecting the conductive state of the polished face of the substrate to be worked 106 held by the hold part 104 via a plurality of conduction parts 109 provided on the polishing pad 103.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polishing pad, a polishing apparatus, and a polishing method, and more particularly to a polishing pad, a polishing apparatus, and a polishing method suitable for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art In recent years, in the field of manufacturing semiconductor devices,
With the increase in density and miniaturization of semiconductor devices, various microfabrication techniques have been researched and developed. Among them, the chemical mechanical polishing (CMP) technology is an indispensable technology when performing the planarization of the interlayer insulating film, the formation of the plug, the formation of the buried metal wiring, and the formation of the buried element isolation. Has become.

[0003] One of the problems in the CMP technique is end point detection. At present, it is common to monitor the friction between the semiconductor wafer surface and the polishing pad during polishing. A method of monitoring this frictional force by a current value of a polishing platen or a motor for rotating a polishing head and detecting an end point from the change has been widely used.

However, depending on the polishing conditions or the film structure of the surface to be polished, the change in the frictional force may not appear remarkably. For example, when the load at the time of polishing is small, a change in the frictional force generally hardly appears.

As another end point detection method, there is a method of optically monitoring. This is for optically measuring the film thickness on the surface of the semiconductor wafer during polishing, and for observing the change in the film type from the reflectivity of the wafer surface.

However, in this method, it is necessary to make light reach the surface of the semiconductor wafer being polished by some means, which involves technical difficulties. In order to make the light directly reach the wafer surface, it is necessary to take measures such as making a hole in the polishing platen to provide a light source and illuminating the overhang position of the semiconductor wafer with light. There is concern that the condition will be adversely affected. In addition, a method of irradiating light in a wavelength region passing through the semiconductor wafer from the back side of the semiconductor wafer is also conceivable. However, providing such a device in the polishing head is expected to have high technical hurdles.

[0007]

As described above, end point detection is one of the problems in the CMP technique, but the conventional end point detection method has not always been satisfactory.

An object of the present invention is to provide a polishing pad, a polishing apparatus and a polishing method capable of easily and reliably detecting an end point in polishing such as CMP. And

[0009]

A polishing pad according to the present invention is a polishing pad used for polishing a surface of a substrate to be processed, and has a plurality of conductive portions spaced apart from each other in a plane direction.

A polishing apparatus A according to the present invention comprises: a polishing table on which a polishing pad having a plurality of conductive portions spaced apart from each other in a surface direction is mounted; and a polishing surface of the substrate to be processed while holding the substrate to be processed. A holding unit that faces a polishing board on which a polishing pad is mounted, a driving unit that relatively moves the polishing board and the holding unit, and a conductive state of a polished surface of a substrate to be processed held by the holding unit. And a detecting unit for detecting through a plurality of conductive portions of the polishing pad.

According to the present invention, a conductive film such as a metal film formed on a substrate to be processed (other than a metal film, any conductive film may be used. For example, a semiconductor film such as polysilicon may be used. In the polishing step, the conductive state of the surface to be polished of the substrate to be polished is detected via a plurality of conductive portions, so that the end point of polishing can be easily and reliably detected by a simple method. Becomes Therefore, appropriate polishing can be performed without insufficient or excessive polishing.

It is preferable that the plurality of conductive portions be arranged concentrically or in a scattered manner. In particular, when the plurality of conductive portions are arranged in a scattered manner, a polishing pad can be produced at a relatively low cost.

Further, by forming the plurality of conductive portions using a conductive polymer resin, the properties of the polishing pad surface can be made similar between the conductive portion and the region other than the conductive portion. The effect on the polishing characteristics can be reduced.

It is preferable that the detecting section detects a conductive state of a polished surface of a substrate to be processed by applying a high-frequency voltage between the plurality of conductive sections.
By applying a high frequency voltage, the electrolysis of the slurry and the corrosion of the metal film on the substrate to be processed due to the electrolysis can be prevented, and even when the contact between the conductive part and the surface to be polished is not perfect, the capacitance can be reduced. The coupling makes it possible to detect the conductive state.

The polishing apparatus B according to the present invention has a plurality of conductive portions spaced apart from each other in the surface direction, and the tips of the plurality of conductive portions are formed as protruding portions protruding from the surface on which the polishing pad is mounted. A polishing plate on which a polishing pad provided with a plurality of holes corresponding to the protrusions of the plurality of conductive portions is mounted, and the polishing pad is mounted on a surface to be polished of the substrate to be processed while holding the substrate to be processed. A holding unit that faces the polished plate, a driving unit that relatively moves the polishing plate and the holding unit, and a conductive state of the surface to be polished of the substrate to be processed held by the holding unit, the plurality of conductive members. And a detection unit that detects the signal via the unit.

According to the present invention, similarly to the polishing apparatus A, the conductive state of the surface to be polished of the substrate to be processed is detected through a plurality of conductive portions, so that the end point of polishing can be easily and reliably detected by a simple method. It is possible to do. Further, since the polishing pad is not provided with a conductive portion, and a plurality of holes corresponding to the protrusions of the plurality of conductive portions provided on the polishing board may be provided in the polishing pad, the polishing pad can be produced at lower cost. it can.

The polishing apparatus C according to the present invention has a plurality of conductive portions which are spaced apart from each other in the plane direction and has a polishing surface having a polished surface, and a substrate to be processed which holds the substrate to be processed. A holding unit for causing the polishing surface to face the polishing surface of the polishing machine; a driving unit for relatively moving the polishing machine and the holding unit; and a conductive state of the surface to be polished of the substrate to be processed held by the holding unit. And a detecting unit for detecting through the plurality of conductive units.

According to the present invention, similarly to the polishing apparatus A, the conductive state of the surface to be polished of the substrate to be processed is detected through a plurality of conductive portions, so that the end point of polishing can be easily and reliably detected by a simple method. It is possible to do.

In the polishing apparatuses B and C, the plurality of conductive portions are preferably arranged concentrically or in a scattered point. Can be produced in Further, similarly to the polishing apparatus A, it is preferable to apply a high-frequency voltage between the plurality of conductive parts.

In the present invention, the concept of polishing includes:
In addition to CMP, grinding using a grindstone is also included.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a view schematically showing a schematic configuration of a polishing apparatus according to a first embodiment of the present invention. FIG. 1 (a) shows the polishing apparatus viewed from the side. Schematic diagram, FIG.
(B) is the schematic which looked at the principal part of the apparatus from the top.

As shown in FIG. 1, the polishing platen 101 rotates in a direction indicated by an arrow in a horizontal plane about a polishing platen rotating shaft 102, and a polishing pad 103 is provided on a main surface thereof. It is to be attached.

Above a position eccentric from the center of the polishing platen 101, a holding portion 104 of the semiconductor wafer is disposed, and the same direction as the polishing platen 101 in a horizontal plane about a holding portion rotating shaft 105 of the semiconductor wafer. It is designed to rotate.
The lower surface of the semiconductor wafer holding unit 104 holds a semiconductor wafer 106 to be polished by a vacuum chuck or the like. Then, a driving mechanism such as a cylinder is pressed with a constant pressure so that the polished surface of the held semiconductor wafer 106 comes into contact with the polished surface of the polishing pad 103.

Above the center of the polishing platen 101, a slurry supply pipe 107 is provided.
From 7, the slurry 108 is supplied onto the polishing pad 103.

In the polishing pad 103, two polishing pad conductive portions 109 are concentrically embedded in the polishing pad main body (insulator) so as to be separated from each other. The distance between the two conductive portions 109 is set so as to make contact with the conductive portion 109. The terminals 110 of the current monitor 111 come into contact with the two conductive portions 109, and the current monitor 11
1 applies a high frequency voltage. Current monitor 11
1 monitors the current flowing between the two conductive portions 109, and can control the CMP operation based on the monitoring result.

FIG. 2A is a diagram showing a cross-sectional configuration of a semiconductor wafer 106 subjected to a CMP process by the polishing apparatus shown in FIG. That is, the silicon oxide film 11 is formed on the main surface side of the semiconductor wafer 106, and the metal film 12 is formed so as to fill the trench for wiring formed in the silicon oxide film 11. In this example, it is assumed that a damascene wiring as shown in FIG. 2B is formed by CMP on the device surface having such a structure.

Holding section 10 holding semiconductor wafer 106
4 (rotation speed: 50 rpm) is applied to the polishing platen 101 (rotation speed: 50 rpm) to which the polishing pad 103 is attached.
Press at 00 g weight / cm ² . At the same time, a slurry 108 is dropped from the slurry supply pipe 107 onto the polishing pad 103 at a rate of 200 ml / min. Slurry 1
For example, when the metal film 12 is tungsten, a material obtained by dissolving about 8 wt% of ferric nitrate in an alumina dispersion liquid is used as 08. Thus, the CMP of the device surface of the semiconductor wafer 106 is performed with the slurry 108 interposed between the semiconductor wafer 106 and the polishing pad 103.

When the metal film 12 is provided on the entire device surface of the semiconductor wafer 106, the two conductive portions 109
Although a large amount of current flows between them, the resistance increases as the metal film 12 becomes thinner, so that the current flowing between the two conductive portions 109 gradually decreases. Then, after the metal film 12 in the region other than the groove is completely removed, the current value becomes constant at a low level. Therefore, the end point of polishing can be detected from such a current change.

FIG. 3 is an equivalent circuit of the present system. The resistance of the conductive part 109 is denoted by r, the surface resistance of the semiconductor wafer 106 between the conductive parts 109 is denoted by r _w , and the resistance between the conductive parts 109 related to the ion conduction of the slurry on the polishing pad 103 is denoted by r _i . Resistance r _w and the resistor r _i becomes parallel, and form the resistor r is connected in series with the parallel portion.
The resistance r _w is a variable resistance whose resistance increases as the metal film thickness is reduced by CMP, and the resistance changes from about 1Ω to infinity. The resistance r is about 10Ω,
The resistance r _i varies depending on the type and concentration of the electrolyte in the slurry, but is roughly 100Ω.

FIG. 4 shows how the current (effective value) changes with polishing time in the above system. Assuming that the thickness of the metal film decreases at a constant rate, that is, the metal film is polished at a constant polishing rate,
This is the result of calculation.

The current border t _c of the region is constant and decreasing region, the time the extra metal film has just been removed. In this calculation, the in-plane uniformity is idealized,
The time at which the metal has just been removed is the same at any location on the wafer. Further, the thin film effect when the metal film thickness is reduced, that is, the increase in resistance due to electron scattering at the interface is ignored. Therefore, the current change in the vicinity of t _c is generally not critical, unlike the calculation. Therefore, in consideration of this point, it is preferable to end the polishing with a margin of about 10% longer than the time determined to be just.

The voltage V applied between the conductive parts 109 is within an observable range considering that the slurry does not cause electrolysis and that the metal film on the semiconductor wafer 106 does not corrode with the electrolysis. It is better to be as small as possible. It is appropriate to use a voltage of about mV order or less. For the above reason, the voltage applied between the conductive portions 109 is preferably a high frequency, and ideally about 10 kHz.

For the conductive portion 109 of the polishing pad, a mixture of a conductive material and a synthetic resin is used, or a polymer compound having semiconductor properties is used. The former is a thermoplastic resin or thermosetting resin, conductive powder such as Au, Ag, Cu, Ni, carbon black, graphite, or foil, metal fiber, conductive fiber such as carbon fiber, a large amount was blended Things are equivalent.

The method of processing the conductive portion 109 is as follows.
A method in which a portion where the conductive portion of the polishing pad is provided is cut out in a ring shape and the conductive portion is buried, or a method in which a portion where the conductive portion of the polishing pad is provided with a conductive material is selectively conceivable. There may be a case where the conductive portion is provided only on the upper layer of the multilayer polishing pad.

The material required for the conductive portion 109 is that the electric resistance is sufficiently small and that the polishing characteristics are not affected. In order not to affect the polishing characteristics, it is preferable that the material of the surrounding polishing pad is similar in elasticity and viscoelasticity. In addition, in order to prevent a step from occurring between the conductive portion and the periphery of the conductive portion, the reduction in polishing or dressing is made equal between the two. In addition, a material that does not elute components that cause wafer contamination after CMP is selected. Further, it is needless to say that hard and large particles that cause scratches during polishing are not included.

Care must also be taken in how the terminal 110 contacts the conductive portion 109. Increased contact resistance due to insufficient contact should be prevented. A device such as pressing with a spring is required, and a device such as the shape of the terminal is required. In addition, since the terminal 110 generally comes into contact with a strongly oxidizing, strongly acidic or strongly alkaline slurry, a material having chemical resistance is selected. It may be coated with a chemically safe metal such as Pt.

(Embodiment 2) FIG. 5 is a view schematically showing a schematic configuration of a polishing apparatus according to a second embodiment of the present invention. FIG. 5 (a) shows the polishing apparatus viewed from the side. Schematic diagram, FIG.
(B) is the schematic which looked at the principal part of the apparatus from the top.

As shown in FIG. 5, the polishing platen 201 rotates in a direction indicated by an arrow in a horizontal plane about a polishing platen rotating shaft 202, and a polishing pad 203 is provided on a main surface thereof. It is to be attached.

Above a position eccentric from the center of the polishing platen 201, a holding portion 204 for the semiconductor wafer is disposed, and the semiconductor wafer holding portion rotating shaft 205 is centered in the same direction as the polishing platen 201 in a horizontal plane. It is designed to rotate. The semiconductor wafer holding section 204 holds a semiconductor wafer 206 to be polished on its lower surface by a vacuum chuck or the like. Then, a driving mechanism such as a cylinder is pressed with a constant pressure so that the polished surface of the held semiconductor wafer 206 comes into contact with the polished surface of the polishing pad 203.

A slurry supply pipe 207 is disposed above the center of the polishing platen 201.
7, the slurry 208 is supplied onto the polishing pad 203.

In the polishing pad 203, two columnar polishing pad conductive portions 209 are embedded in the polishing pad body (insulator) at a distance from each other, and the surface of the semiconductor wafer 206 is polished during polishing. The distance between the two conductive parts 209 is set so as to contact the conductive parts 209.

The two conductive portions 209 are provided on the polishing platen 20.
1 are electrically connected to the conductive columns 212 provided therein. A conductive wire 214 is electrically connected to the conductive column 212 on the back side of the polishing platen 201. This conductor 214
Rotary terminal 21 provided around polishing platen rotary shaft 202
5, and a high-frequency voltage is applied to the rotating terminal 215 from the current monitor 211 via the terminal 210. The current monitor 211 monitors the current flowing between the conductive units 209, and can control the CMP operation based on the monitoring result. When the polishing table 201 is a conductor, it is necessary to provide an insulating tube 213 around the conductive column 212. When the polishing platen rotating shaft 202 is a conductor, an insulator is provided between the rotating plate 202 and the rotating terminal 215.

The voltage applied between the conductive portions 209, the material of the conductive portion 209, and the processing method are the same as in the first embodiment.

As in the first embodiment, CMP is performed on the substrate as shown in FIG. 2A under the same conditions as those in the first embodiment, and FIG. It is assumed that a damascene wiring as shown is formed.

In a time zone A during which the polishing platen 201 rotates during polishing and the semiconductor wafer 206 and the two conductive portions 209 are in electrical contact, the electric conduction on the surface of the semiconductor wafer 206 and the semiconductor wafer 206 The ion conduction of the slurry interposed between the polishing pads 203 is reflected. on the other hand,
In the time zone B in which the semiconductor wafer 206 and the two conductive portions 209 are not in electrical contact, only the ion conduction of the slurry on the polishing pad 203 is reflected.

In the time zone A, when the metal film 12 is present on the entire device surface, the two conductive portions 2
Although a large amount of current flows between the two conductive portions 209, the current flowing between the two conductive portions 209 gradually decreases because the resistance increases as the metal film 12 becomes thinner. After the metal film 12 in the region other than the groove is completely removed, the current value is constant at a low level of only the ionic conduction of the slurry. In the time zone B, the current value is constant at a low level of only the ionic conduction of the slurry, regardless of the thickness of the metal film 12 on the device surface.

Therefore, the current (effective value) in this example
The change becomes pulse-like (appears in time zone A). The period of this pulse is 1.2 sec because the rotation speed of the polishing platen 201 is 50 rpm. Then, the height of this pulse gradually decreases. Although it becomes pulse-shaped, the basic current change is the same as in FIG. 4, and the end point of polishing can be detected as in the first embodiment.

It is preferable that the contact resistance between the conductive portion 209 and the conductive column 212 is small. However, when a high frequency of a certain level or more is applied, a capacitor may be interposed by a slight gap. With this in mind,
A configuration in which the conductive portion 209 is not provided on the polishing pad 203 is also feasible.

FIG. 6 is a diagram schematically showing a schematic configuration of a polishing apparatus having such a configuration. Components corresponding to the components shown in FIG. 5 are denoted by the same reference numerals. I have.

In the structure shown in FIG. 6, the upper part of the conductive column 212 is projected from the upper surface of the polishing
The polishing pad 203 is provided with a hole corresponding to the protrusion 212a. The polishing pad 203 is adhered on the polishing platen 201 through the protrusion 212 a through the hole.
The height of the upper surface of the projecting portion 212a is slightly lower than the upper surface of the polishing pad 203, and the upper surface of the conductive column 212 (the upper surface of the projecting portion 212a) is prevented from being corroded by the slurry. The upper surface is covered with a thin insulating plate 221. The insulating plate 221 having a large dielectric constant is used. In addition, this insulating plate 221 is
It may be provided on the polishing pad 203 side.

As described above, according to the configuration shown in FIG.
Since it is only necessary to provide a hole through which the conductive column passes without providing the conductive portion on the polishing pad, there is an advantage that the polishing pad can be produced at low cost.

In each of the examples described above, CMP has been described. However, the present invention is similarly applicable to grinding using a grindstone. When using a whetstone, basically
It is possible to take a configuration similar to each example of the CMP described in FIG. 6 to FIG. 6, for example, a configuration as shown in FIG. In the example illustrated in FIG. 7, a polishing platen is configured by the grindstone 231, and the upper surface of the grindstone 231 is used as a polishing surface, and the conductive pillar 232 is provided in the grindstone 231. As in the example shown in FIG. 6, the upper surface of the conductive column 232 may be covered with a thin insulating plate.

In the first and second embodiments described above, two conductive portions (conductive portions and conductive columns of the polishing pad) are provided. However, the number of conductive portions is further increased to increase the surface of the semiconductor wafer. When a large number of contacts are made, the degree of scraping of the center and the periphery of the wafer, that is, the in-plane uniformity of the CMP can be monitored.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and can be variously modified and implemented without departing from the gist of the present invention.

[0056]

According to the present invention, the end point of polishing can be easily and reliably detected by a simple method by detecting the conductive state of the surface to be polished of the substrate to be processed through a plurality of conductive portions. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a schematic configuration of a polishing apparatus according to a first embodiment of the present invention.

FIG. 2 is a view showing an example of a polishing process using the polishing apparatus according to the present invention.

FIG. 3 is a diagram showing an equivalent circuit in a main part of the polishing apparatus according to the present invention.

FIG. 4 is a diagram showing a change in current with respect to a polishing time when polishing is performed by the polishing apparatus according to the present invention.

FIG. 5 is a diagram schematically showing a schematic configuration of an example of a polishing apparatus according to a second embodiment of the present invention.

FIG. 6 is a diagram schematically showing a schematic configuration of another example of the polishing apparatus according to the second embodiment of the present invention.

FIG. 7 is a diagram schematically showing a schematic configuration of another example of the polishing apparatus according to the third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Silicon oxide film 12 ... Metal film 101, 201 ... Polishing surface plate 102, 202 ... Rotation axis 103, 203 ... Polishing pad 104, 204 ... Holder 105, 205 ... Rotation axis 106, 206 ... Semiconductor wafer 107, 207 ... Slurry supply pipes 108, 208 Slurries 109, 209 Polishing pad conductive parts 110, 210 Terminals 111, 211 Current monitors 212, 232 Conductive pillars 212a Projecting parts 213 Insulating pipes 214 Conductive wires 215 Rotating terminals 221 Insulating plate 231 ... Whetstone

Claims (13)

[Claims] 1. A polishing pad used for polishing a surface of a substrate to be processed, comprising: a plurality of conductive portions which are separated from each other in a plane direction. 2. The polishing pad according to claim 1, wherein the plurality of conductive portions are arranged concentrically. 3. The polishing pad according to claim 1, wherein the plurality of conductive portions are arranged in a scattered manner. 4. The polishing pad according to claim 1, wherein the plurality of conductive portions are formed using a conductive polymer resin. 5. A polishing disk on which the polishing pad according to claim 1 is mounted, and a polishing disk holding a substrate to be processed and a polishing surface of the substrate to be polished mounted with the polishing pad. A driving unit that relatively moves the polishing plate and the holding unit; and a plurality of conductive members that the polishing pad has to determine the conductive state of the surface to be polished of the substrate to be processed held by the holding unit. A polishing apparatus, comprising: a detection unit that detects through a unit. 6. The apparatus according to claim 5, wherein said detecting section detects a conductive state of a polished surface of a substrate to be processed by applying a high frequency voltage between said plurality of conductive sections. The polishing apparatus according to the above. 7. A polishing method using the polishing apparatus according to claim 5 or 6, wherein the substrate to be processed held by the holding portion is polished by the polishing pad mounted on the polishing board. A polishing method, wherein the detection unit detects a conductive state of a surface to be polished of a substrate to be processed held by a holding unit via a plurality of conductive units of the polishing pad. 8. A plurality of conductive portions having a plurality of conductive portions which are separated from each other in a plane direction, and tips of the plurality of conductive portions project from a surface on which a polishing pad is mounted. A polishing pad on which a polishing pad provided with a plurality of holes corresponding to the projections of the polishing pad is mounted, and a substrate to be processed is held and the surface to be polished of the substrate is opposed to the polishing pad on which the polishing pad is mounted. A holding unit, a driving unit that relatively moves the polishing board and the holding unit, and a detection that detects a conductive state of a polished surface of the substrate to be processed held by the holding unit via the plurality of conductive units. A polishing apparatus comprising: a unit; 9. The apparatus according to claim 8, wherein said detecting section detects a conductive state of a polished surface of a substrate to be processed by applying a high frequency voltage between said plurality of conductive sections. The polishing apparatus according to the above. 10. A polishing method using the polishing apparatus according to claim 8 or 9, wherein the substrate to be processed held by the holding section is polished by the polishing pad mounted on the polishing board. A polishing method, comprising: detecting a conductive state of a surface to be polished of a substrate to be polished held by a holding unit by the detection unit via the plurality of conductive units. 11. A polishing plate having a plurality of conductive portions spaced apart from each other in a plane direction and having a polished surface, and a polished surface of the polished disk holding a substrate to be processed and a polished surface of the substrate. A holding unit opposed to a polishing surface, a driving unit for relatively moving the polishing board and the holding unit, and a conductive state of the surface to be polished of the substrate to be processed held by the holding unit, the plurality of conductive units A polishing apparatus, comprising: a detection unit that detects the electric current through the polishing apparatus. 12. The apparatus according to claim 11, wherein said detecting section detects a conductive state of a polished surface of a substrate to be processed by applying a high frequency voltage between said plurality of conductive sections. The polishing apparatus according to the above. 13. A polishing method using the polishing apparatus according to claim 11, wherein the substrate to be processed held by said holding portion is polished by a polishing surface of said polishing board, and held by said holding portion. A polishing method, wherein the detecting unit detects the conductive state of the polished surface of the substrate to be processed via the plurality of conductive units.